摘要:
品质因子( Q)是反映地层对地震波吸收衰减强弱的重要参量。在强衰减条件下,常规方法估算(如谱比法等)的品质因子往往比物理定义的品质因子下限(2π)还小。通过考察两者差异的来源,给出了两者的换算公式。模型测试表明,当品质因数小于30时,常规估算品质因子和物理定义品质因子的相对误差将超过10%,两者应加以区分,不可混用。根据两种品质因子的特点,有如下建议:当拟合Q?V经验式时,使用物理定义品质因子;当进行反Q补偿时,使用常规估算品质因子;当对同一工区的品质因子进行对比时,应换算成同一类品质因子。
Abstract:
Quality factor ( Q) is a key parameter for geophysical exploration in that it indicates the magnitude of sediment attenuation. When attenuation is large,quality factor computed by conventional methods such as spectral ratio method is smaller than 2π,which is the low limit of Q calculated by defining expression. Conversion formula for the two quality factors is introduced by investigating the differences between them.Model tests indicate that,when quality factor is lower than 30,relative error between quality factors calculated by two methods is larger than 10% so that they should be distinguished one from another.Based on this study,the authors put forward some advises.First,during Q?V fitting process,it is prefer to use the quality factors calculated by defining expression.Second,convention?al method is preferred in gaining quality factors in reverse Q compensation process.Third,when the comparison of quality factors is nee?ded in an oil field,quality factors should be converted to the same class before the comparison.
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